Literature review highlights myth surrounding herbicides, pesticides

September 25, 2012
- by
Keith Nunes

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The literature review conducted by researchers at Stanford University’s Center for Health Policy comparing the nutritional quality and safety of organic foods with those products produced in a conventional fashion has generated a lot of discussion in the food industry and in the mainstream media. Of great importance, the findings highlight a fundamental misunderstanding about the role herbicides and pesticides play in conventional agriculture.

The study was published Sept. 4 in the American College of Physicians’ Annals of Internal Medicine. The researchers, according to the study, reviewed thousands of papers and identified 237 of the most relevant to analyze. Those include 17 studies, 6 of which are randomized clinical trials, of populations consuming organic and conventional diets, and 223 studies that compare either the nutrient levels or the bacterial, fungal or pesticide contamination of various products, including fruits, vegetables, grains, meats, milk, poultry, and eggs, grown organically and conventionally.

After analyzing the data, the researchers found little significant difference in health benefits between organic and conventional foods. No consistent differences are noted in the vitamin content of organic products, and only one nutrient — phosphorus — is significantly higher in organic versus conventionally grown produce. The researchers note that because few people have a phosphorous deficiency, it has little clinical significance. There is also no difference in protein or fat content between organic and conventional milk, though the data indicate evidence exists from a limited number of studies suggesting organic milk may contain higher levels of omega-3 fatty acids.

The researchers were also unable to identify specific fruits and vegetables for which organic appears the consistently healthier choice.

The review also yields little evidence conventional foods pose greater health risks than organic products. While the researchers found organic produce has a 30 per cent lower risk of pesticide contamination than conventional fruits and vegetables, organic foods are not necessarily 100 per cent free of pesticides. The researchers also note that the pesticide levels of all foods generally falls within the allowable safety limits.

Two studies of children consuming organic and conventional diets did find lower levels of pesticide residues in the urine of children on organic diets, though the significance of the findings on the health of the children is considered unclear. Additionally, organic chicken and pork appear to reduce exposure to antibiotic-resistant bacteria, but the clinical significance of the finding is also determined to be unclear.

In discussing limitations of the literature review, the researchers point to the heterogeneity of the studies they reviewed due to differences in testing methods; physical factors affecting the food, such as weather and soil type; and great variation among organic farming methods. With regard to the latter, there may be specific organic practices, for example, the way that manure fertilizer, a risk for bacterial contamination, is used and handled, that may yield a safer product of higher nutritional quality.

What is instructive about the study’s results is the widespread belief that the use of pesticides and herbicides may reduce or limit the nutritional quality of the crops to which they are applied. In fact, the assumption should be exactly the opposite.

Pesticides and herbicides were developed to allow crops to grow unencumbered by some weeds, plant diseases or pests. By deterring specific organisms, pesticides and herbicides allow plants to reach maturity more quickly.

The results are consistent crop quality and larger yields. The notion such growing conditions may limit the development of nutrients and vitamins within a plant, especially when it is compared to a plant that has been grown in an organic fashion, doesn’t hold up under scientific scrutiny.

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